During the last ten years, many efforts have been made to find new types of catalysts, either in the zeolitic field, or in the crystalline silica field.
One problem with zeolitic type catalysts is that they are subject to rapid deactivation in the presence of even small amounts of water. Rapid deactivation means that a high rate of conversion of reactants to products cannot be maintained over a long period of time thus requiring expensive catalyst changeouts or regeneration procedures which greatly reduce the efficiency of the overall process.
More recently, crystalline silicas of the silicalite type, as prepared in U.S. Pat. No. 4,061,724, have been recognized to be of the orthorhombic symmetry and to have steam stability.
It has also been recently reported that silicalite type crystalline silicas exhibit some shape selectivity in the presence of steam. Greater shape selectivity than is obtainable with such previously existing materials would be desirable.
The Applicants have disclosed in a co-pending application that crystalline silicas of monoclinic symmetry have interesting shape selective properties.
There is, therefore, a need for a process to prepare a crystalline silica catalyst having the monoclinic symmetry.